Expansible pulley.



No. 792,220. V PATENTED JUNE-13, 1905.

- L. J JOHNSTON.

EXPANSIBLE PULLEY.

APPLICATION TILED MAY 13, 1903.

UNITED STATES Patented June 1 3, 1 905.

LEUNE J. JOHNSTON, OF PETALUMA, CALIFORNIA.

EXPANSIBLE PULLEY.

SPECIFICATION forming part of Letters Patent N 0. 792,220, dated June 13, 1905. Application filed May 13,1903. Serial No. 156,861.

To all whom it may concern.-

Be it known that I, LEUNE J. JOHNSTON, a citizen of the United States, residing at Petaluma, county of Sonoma, State of California, have invented an Improvement in Expansible Pulleys; and I hereby declare the following to be a full, clear, and exact description of the same.

My invention relates to an improvement in power-transmission devices wherein the driving-pulley may be expanded or contracted in diameter and the driven pulley actuated by a driving chain, belt, or rope may be correspondingly contracted or expanded, so as to change the rate of speed.

My invention is an improvement upon a patent, No. 679,076, issued to me July 23, 1901 and it consists of the parts and the constructions and combinations of arts, which I will hereinafter describe and c aim.

Figure 1 is a plan view showing a pair of adjustable pulleys with my improvements. Fig. 2 is an enlarged section of one of the blocks with its sprocket-tooth engaging a chain-link. Fig. 3 is an exterior side view of the block, showing the guides. Fig. 4 is a top view of the block. Fig. 5 is a vertical section of the rim, showing two of the radial arms and a block 6 guided thereon. Fig. 6 is an edge view of the rim-flanges, showing the ends of the radial arms dovetailed into corresponding channels in the block.

In my present inventionAA are shafts having disks 2 3 slidable upon the shafts, and these disks being of different diameter are united by cones of rods 4, which converge from the larger to the smaller disks.

The pulleys through which power is communicated consist of rims or disks 5, fixed in pairs upon the shafts A and having blocks or segments 6 perforated, so that they may slide upon 'the rods and at the same time so guided as to move radially outward or inward between the wheels or disks which carry them. These segments are of such size and so disposed that theyform the peripheryof the pulley about which the belt,rope, or chain passes and through which power is communicated.

The disks or rims carrying the cones of rods previously described are connected by a centrally-pivoted clutch-lever or equivalent actuating device, as at 7, so that when this lever is moved one cone will be caused to slide through the blocks through which the rods pass in the direction to move these blocks outwardly and increase the diameter of the bearing-surface, while the other rods will correspondingly contract the blocks through which they pass and decrease the diameter of the belt surface or rim in exact relation with the increase of the first-named rim, so that a belt, chain, or rope passing around these pulleys will always remain sufiiciently tight to transmit power, but the rate of transmission will be varied in proportion as the pulleys are enlarged and contracted.

In this invention the guides for the radially-slidable blocks 6 consist of spokes or arms 11, extending outwardly to the rims 5, as shown in Fig. 5. The exterior rims are set out from the spokes, so that the spokes 11 practically extend up to the periphery inside the planes of the rims.

The blocks 6have a curved peripherywhich forms the surface over which the driving belts or chain passes, and these blocks have lugs formed upon them, as shown at 9 and 10. These lugs are so disposed, projecting in each direction, as to clasp the radial guiding-spokes 1 1, between which they are movable, and the lugs 9 and 10 do not extend out so far as to contact with the offset rims 5. Thus when free the blocks can be slid in or out Without in any way disturbing the rims, and it is only necessary to remove the particular guide-rod 4, Whichpasses through the block. These guiderods pass through holes a, made in the blocks at the same angle as the angle of convergence of the rods. I have shown these blocks preferablymade with the rim having an intervening channel or space between the sides. If the pulleys are designed to carry smooth belts or ropes, the surfaces of these blocks 6 are suflicient to provide the required frictional adhesion to transmit power. In this case the pulleys may have a third flange 5, between which and the adjacent flange 5 the belt runs. l/Vhen a sprocket-chain is used having links of substantially equal size, it will be manifest that the links if fitted to equally-spaced sprocket-teeth for a certain diameter of rim would not fit those sprocketteeth when the diameter of the rim was changed. I have therefore shown the engaging sprocket-teeth 12 as made with a periphery similar to that of the rim-blocks 6, and the edges of said plates converge toward the center and are pivoted between the sides of the rim-blocks 6, as shown at 3. The interior angles 1) of these teeth form stops to contact with the bottoms of the slots and limit the tilt of the teeth in either direction. The opposite points of the plates 12 are slightly above the peripheral surface of the blocks 6, and as the chain passes it will engage the point toward which the chain is moving. It will, however, be manifest that not all of the links of the chain will always be engaged by these points on account of the varying distance between them. Consequently those links of the chain which do not engage with these sprocket-points will simply rest upon the curved peripheral surface and travel around the pulley in this position. There will always be enough of the chainlinks engaged with these sprocket teeth, however, to transmit power as fully as is needed. Any reversal of the driving will tilt the sprocket-teeth in the opposite direction, and the links will then engage with the opposite points of these teeth.

In some cases where the driving-chain is applied to automobiles or in other places where a very considerable power is necessary and where the strain may tend to spread the guides between which the blocks 6 arev slidable 1 have found it advisable to fix the rims 5 to the radial guiding-rods 11 in such a manner that the ends of the blocks 6 may be bored to inclose and clasp the rods, so as to form a positive connection between them,

and thus prevent the spreading of the rims. This construction is shown in Fig. 6.

Having thus described my invention,what I claim, and desire to secure by Letters Patent, is

1. An improved expansible pulley having in combination radially extending arms, rims at the ends of the arms and having their inner faces abutting the outer faces of the arms whereby the arms extend up inside the plane of the inner faces of the rims to substantially the periphery thereof, sections of a width corresponding to the distance between the inner faces of the arms said sections guided on the arms and removable endwise through the space at the top between adjacent rims, said sections having surfaces to engage with a flexible driving band, and means by which the sections are simultaneously expanded or contracted.

2. An improved expansible pulley having in combination radially disposed arms, a hub, and a shaft to which the hub is fixed, rims at the outer ends of the arms and in the plane of the outer faces thereof whereby the arms extend up along the inner faces of the rims to the periphery thereof, sections slidably fitting the inner faces of the arms and removable through the space at the top between adjacent rims and members within the sections and having projecting points at each end, said members being pivoted and tiltable within the blocks to present either point to engage with the power-transmitting chain.

In witness whereof I have hereunto set my hand.

LEUNE J. JOHNSTON. Witnesses:

S. H. N oURsE, HENRY P. TRICOU. 

